Radiostabilizer



I. A. SOWDER RADIOSTABILIZER Nov. 30 1926.

Filed June 24 1925 25heets-Sheet 1 WLEWQT 614201 wimp.

SACKETT E1 WILHELMS CORP NY mom LITHO by Nov. 30,1926. 1,608,964 I. A. SOWDER RADIOSTABILIZER Filed June 24 1 25 2'Shee tsSheei; 2

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Patented Nov. 30, 1926.

NITED STATES ISAAC A. so'wnnn, or oHAr'rAnooGA, r'nnnnssnn, assisnon are n. M. srnwann MANUFACTURING COMPANY, me, or. cnsr'ranooea, rnlvnnssnn, a 'oonrona- TION OF TENNESSEE.

RAnIosrABILI'znn,

. Application filed June 24, 1925. Serial No. 39,321.

This invention relates'to improvements in radio apparatus, and more particularly to 7 means ofstabilizin tuned circuits for the amplification of ra iofrequency oscillations. It has heretofore been proposed to'employ electron discharge tubes connected in cascade for the amplification of radiofrequency oscillations, and t'o-etfect'the successive connections between the respective tubes by 10 means of transformers. The resistances of such circuits are substantially constant, but the impedances of/the. external circuitsvary as theapparatus istuned for the various frequenc1es.f"The tendency therefore is for the apparatusto become unstable as an amplifier at the higher frequencies correspondmg to wave-lengths of about 300 meters, depending u n the losses in the particular apparatus. he apparatus at such an unstab e-point was critical and was easily thrown into continuousgoscillation.

prevent the occurrence of such critical points within the ran 'e Of' frequencies employed at the present ay forbroadcasting. Such means have been of the loss stabilizer type in which the operation depended upon the introduction of a 'loss by purely ohmic resistance into the grid circuit of the apparatus: or of the balancing or neutralizing types, in which the capacity of the tube itself was balanced out by a shunting condenser, and the other impedance effects were compensated by split inductances and the so like.

, The conp ensation of the set requires a continuousadjustment for each wave-length to be received. With loss stabilizers, the resistance introduced was usually of the po- 40 tentiometric type, and advanced by steps,

so that no regular gradation to suit the va rious waves was attainable. Furthermore, with many such circuits, the inclusion of a 'certain portion of the loss resistance was necessary for the operation of the apparatus even at higher wave-lengths. With balancing systems, it is'usually necessary to bal ance each tube separately: andusually once so for all at one of the desired wave-lengths.

bilizer is provided for radiofrequenc amplifiers, which enables the operation 0 the ap- According to the present invention, a sta'-.

paratus atsubstantial resonance at any wavelength; and allows the operator to immediately andexactly eliminate any tendency tential of the stabilizer mechanism with, re

spect to the coils is defined. 7

By way of illustration, this invention is demonstrated in connection with an apparatus employing two radiofrequency amplifying tubes and a detector, but it will be understood that such arrangement is a not compulsory, and that more or less tubes may be employed, and that the currents from the amplifying apparatus may be used for any purpose'desired. Various means have been suggested to In the drawings: Fig. 1 shows a diagram of .such a circuit, with a stabilizer app ied to the grid transformer of the second radiofrequency amplifying tube. a t Fig. 2 shows a top plan of'such an appara- Fig. 3 shows the corresponding rear View. Fig. 4 shows a support imperspective.

The antenna 10. is connected through an inductance 11 to the ground at 12. This in ductance 11 constitutes the primary of a transformer T, having the secondary 18 which may be tuned by the variable condenser 14, andhas one terminal connected to the grid of the first radiotrequency ampli fying electron discharge tube A, and the otherterminal connected to the filamentary cathode of this same tube.

The plate of this tube A is connected to the reversed primary 15 ofa second transformer T and thence to the common plate battery conductor 16, the commonplate battery 17, and by the returnhus wires 18, 19, to the cathode of the tube A. This transformer T has a secondary 20 which may be tuned by the variable condenser 21, and has one of its terminals connected to the grid of the second amplifying tube B, and V the other terminal to the filamentary cathode of this same tube B,

The plate of the tube B is connected to the primary 22 of a further transformer T and thence to the common plate battery conductor lfi, the plate battery 17, with a return as before to the filament of the tube B. The transformer T, has a secondary 23 which i may be tuned by a variable condenser 24,

and which has one of its terminals connected through the customary grid leak and condenser 25 to the grid of the detector tube D, and the other terminal connected to the filamentary cathode of this tube D.v

The plate of the tube D is connected through the indicating instrument 26 and wire 27 to an appropriate portion of the plate battery 17, and with a return by wire I 18 to the cathode of the tube D.

The filaments are heated by the single bat- Q i i tery 28. The amplifier tube filaments are and the grouped and controlled by the rheostat 29, detector filament isconnected through a separate rheostat 30. The com- ,I connected 7 to 3 the p s t ment.

i disk of magnetic conductive material mon conductor 31 serves to connect the negative terminals of the amplifier filaments and the grid returns ,of these tubes to the ground.

The grid return of the detector. tube D is side of the an- 'disk 35 in its inmost position is m close parallelism to and concentric with the transforiner T which is-illustrated as being of the air-core, fiat pancake type with Zigzag windings to reduce'the capacity effects. In

,order to closely define the potential of-this disk, it ispreferably connected by the conductor 40 to the common positive bus wire 19 of the amplifier tubes.

'. In operation, as the apparatus is tuned by the variable condensers 14, 21, 24, it is foundthat as the wave-length adjustment becomes lower and lower, the circuits tend more and more'to'set up continuous selfoscillations. The operator can-meet thiscondition by rotating the cam 29' to bring the disk 35' more and more into th field of the transformer inductances 15 aid 20; The

- efiect is to change the efiective impedance of these elements, to producean eddy current loss by the disk of the current circulating'in the inducta'nces, to limit or'confine the, external magnetic fields of these'coils,

and to produce a capacity efi'ect across the tube 3 from vgrid to filament in shunt of the input tuning condenser. As a total results, the tendency towards oscillation is checked: it may be remarkedthat this checking point 5 .very exact and may be located and controlled easily b the operator.

A further and additional advantage of the particular arrangement shown, is that after the set has been stabilized; which as indicated above occurs at a very definite and-certain position for a given wave-length, a further inward movement of the disk will give a very successful regulation or the volume ofthe output.

In Figs. 2 and 3 is shown the employ-' ment of such a circuit and arrangement of apparatus. The transformers T T T are shown as mounted on supports-50, 51, 52 which are bolted to the rear plates 53 of the condensers 14, 21, 24. These supports are shown in detail in Fig. 4, as having the stem 54 to support the coils at a suflicient distance away fr'om'the condensers and other metallic parts of the apparatus, so

that their fields are substantially free rom metal; and the feet 55 bent at right angles to the stem and provided with the apertures 56 to receive clamping bolts; they permit the adjustment of the transformer coils to various mutual positions of distance and angle. In assembling the apparatus, it is found, by trial that at certain relative angles and positions of the two outer transformers, a minimum reactive relation exists: the central transiormer is then located so as to have a minimum reactive relation with the other two coils and especially with regard to the .last transformer coil, and so that it is substantially horizontal. Thedisk 35 is then adjusted in. position so that absolute stability is attained at the lowest wave-length for which the-apparatus is designed, at its inmost'posi-tion. I

To complete this description,=' it has been found upon test that very satisfactory. re-

sults may be obtained if the transformer coils are of .the pancake, diamond-weave, type with ten turns in the primaries and about fifty-five turns in thesecondaries, of one and three-quarters'inches inside and three and three quarters'inches outside'diameter; with a disk one and one half inches in diameter, held parallel to and. about onehalf inch from the central plane of the transformer coils at the inmost and one'and onehalf inches from said position at the outmost position. The thickness of the disk appears to be relatively unimportant. The appara-' tus constructed-with these elements received excellently from 175 to 600 meters.

. It will'be understood that these quantities are merely byway of instruction and that the invention is not limited either thereto nor to the specific arrangement shown, but may be modified therefrom' within the scope of the appended claims.

I claim l a 1. In a system'foramplifying high irequency electrical oscillations occurring in an input circuit, a plurality of electrond scharge tubes including a first and a second amplifying tubeanda detector tube, means tube, circuits to connect said input, said transformers and said tubes in cascade, a variable condenser to tune the mput clrcult of each'tube, said transformers being of the.

flat wound disk type, the secondaries of all of said transformers being wound in the same direction and the primary of the second transformer being wound in opposition to those of the first and the third transformers, supports forsaid transformers to hold them in spaced relation and substantially free from metal in their respective fields, means to adjust the mutual distance andangle of said transformers, a disk of conductive magnetic material in the field of said second transformer coil, a lever to support said disk,- and means to rock said lever to determine the position of said disk with regard to said transformer, and a conductor from said disk to the, positiye. terminal of said exciting means. I Y

2.; In a transformer for radiofrequen'c electricalv oscillations, a flat primary win ing, a flat secondary winding, a disk of 0011-3- ductive magnetic 'material, a lever to support said disk arallelism with said windlngs, a spring to ia'ssaid lever toward one end position and move said disk away from said windings, and 'a rotatable cam to rock said lever against the action of said sprin to move said .disk toward said windin s, sai

disk adapted to, limit the "external eld of said windings, and to'have a capacitative.

relation therewith.

3. In asystem for amplifying high fre- I quency electrical oscillations,.a pluralityof electron discharge tubes, interstage coupling transformers and associated circuits to eonnect said tubes in cascade relation, the primary of one of said transformers bein reversed with respect to its neighbors, a dis of magnetic conductive material in the field of said reversed primary, and means to move said disk toward and away from said primary. In testimony whereof, I aflix my signature.

ISAAC A. SOWDERL 

